Fix migrate-mstest-v1v2-to-v3 skill activation

The frontmatter description said DO NOT USE FOR: ... projects already on
MSTest v3+, which blocked the skill on every scenario where the packages had
already been bumped to 3.x and only the source or settings still needed the
v1/v2-to-v3 fixes (Assert object overloads, DataRow strict typing,
.testsettings -> .runsettings). It also gated the whole skill behind "the user
asks to upgrade MSTest", so a standalone .testsettings conversion never matched.

- Rewrite the description around both entry points (pre-upgrade migration and
  post-upgrade breaking-change fixes) and add the concrete trigger keywords
  those prompts contain: CS1501/CS1503/CS0121, MSTEST0014, LegacySettings,
  DeploymentEnabled, per-test TestTimeout, net5.0. Note that the current runner
  is preserved so "migrate to v3 but keep VSTest" isn't poached by
  migrate-vstest-to-mtp.
- Narrow migrate-mstest-v3-to-v4, which claimed the generic "tests don't
  compile after upgrading MSTest" phrasing and competed for the same prompts.
- Widen the Boundary Gate: a 3.x package version alone no longer ends the
  migration when v1/v2-era settings or errors remain, so the skill actually
  performs the requested edits instead of reporting "already migrated".
- Add a routing row to the test-migration agent for the same case.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Copilot-Session: ad6ff32a-d441-4a7b-b474-2bfaee764740

plugins/dotnet-test-migration/agents/test-migration.agent.md

@@ -46,7 +46,8 @@ Classify the user's request and route to the appropriate skill or agent:
 | User Intent | Route To |
 |---|---|
 | "Upgrade MSTest" / "migrate MSTest" (v1/v2 detected) | `migrate-mstest-v1v2-to-v3` skill |
-| "Upgrade MSTest" / "latest MSTest" (v3 detected) | `migrate-mstest-v3-to-v4` skill |
+| "Upgrade MSTest" / "latest MSTest" (v3 detected, project otherwise clean) | `migrate-mstest-v3-to-v4` skill |
+| Build/test errors or leftover `.testsettings` after a 2.x-to-3.x package bump (packages already read 3.x) | `migrate-mstest-v1v2-to-v3` skill |
 | "Upgrade MSTest" (v1/v2 detected, user wants v4) | `migrate-mstest-v1v2-to-v3` first, then `migrate-mstest-v3-to-v4` |
 | "Migrate to xUnit v3" / "upgrade xUnit" | `migrate-xunit-to-xunit-v3` skill |
 | "Convert xUnit to MSTest" / "switch from xUnit to MSTest" / "port xUnit tests to MSTest" (xUnit v2 or v3 detected) | `migrate-xunit-to-mstest` skill |

plugins/dotnet-test-migration/skills/migrate-mstest-v1v2-to-v3/SKILL.md

@@ -1,21 +1,22 @@
 ---
 name: migrate-mstest-v1v2-to-v3
 description: >
-  Migrate MSTest v1 or v2 test projects to MSTest v3. Use when the user asks
-  to upgrade MSTest and the project has QualityTools assembly references,
-  MSTest.TestFramework/TestAdapter 1.x-2.x, .testsettings, or migration errors
-  after changing those packages to 3.x.
-  USE FOR: upgrading from MSTest v1 assembly references
-  (Microsoft.VisualStudio.QualityTools.UnitTestFramework) or MSTest v2 NuGet
-  (MSTest.TestFramework 1.x-2.x) to MSTest v3, fixing assertion overload
-  errors (AreEqual/AreNotEqual), updating DataRow constructors, replacing or
-  migrating .testsettings to .runsettings, timeout behavior changes, target framework
-  compatibility (.NET 5 dropped -- use .NET 6+; .NET Fx older than 4.6.2 dropped),
-  adopting MSTest.Sdk while moving from v1/v2.
-  First step toward MSTest v4 -- after this, use migrate-mstest-v3-to-v4.
-  DO NOT USE FOR: migrating to MSTest v4 (use migrate-mstest-v3-to-v4),
-  projects already on MSTest v3+, migrating between test frameworks, generic
-  test modernization, or .NET upgrades unrelated to MSTest.
+  Migrate MSTest v1/v2 projects to MSTest v3, and fix v1/v2-to-v3 breaking
+  changes that surface after the packages are already at 3.x.
+  USE FOR: removing v1
+  Microsoft.VisualStudio.QualityTools.UnitTestFramework assembly references;
+  moving MSTest.TestFramework/TestAdapter 1.x-2.x to 3.x, the MSTest
+  metapackage, or MSTest.Sdk; tests that stopped compiling after a 2.x-to-3.x
+  bump -- CS1501/CS1503/CS0121 on Assert.AreEqual/AreNotEqual/AreSame object
+  overloads, DataRow strict type matching (1L vs 1), MSTEST0014, 16+ DataRow
+  arguments; converting .testsettings/LegacySettings to .runsettings
+  (DeploymentEnabled, per-test MSTest TestTimeout); v3 timeout behavior; TFMs
+  v3 dropped (net5.0, .NET Fx below 4.6.2, netstandard1.0). Applies even when
+  the project already references MSTest 3.x, if a v1/v2-era setting or error
+  remains. Keeps the current runner.
+  DO NOT USE FOR: MSTest v4 (use migrate-mstest-v3-to-v4 next), clean v3
+  projects with no v1/v2 leftovers, converting between test frameworks, or
+  VSTest-to-MTP migration.
 license: MIT
 ---
 
@@ -27,22 +28,25 @@ Migrate a test project from MSTest v1 (assembly references) or MSTest v2 (NuGet
 
 - Project references `Microsoft.VisualStudio.QualityTools.UnitTestFramework.dll` (MSTest v1)
 - Project uses `MSTest.TestFramework` / `MSTest.TestAdapter` NuGet 1.x or 2.x
-- Resolving build errors after updating MSTest packages from v1/v2 to v3
+- Resolving build errors after updating MSTest packages from v1/v2 to v3 -- including when the packages already read 3.x and only the source or settings still need fixing
 - Replacing `.testsettings` with `.runsettings`
 - Adopting MSTest.Sdk or in-assembly parallel execution
 
 ## When Not to Use
 
-- Project already on MSTest v3 with no migration-related build errors (fully migrated)
+- Project already on MSTest v3 with no migration-related build errors and no leftover `.testsettings` / `<LegacySettings>` (fully migrated)
 - Upgrading v3 to v4 -- use `migrate-mstest-v3-to-v4`
 - Migrating between frameworks (MSTest to xUnit/NUnit)
 
 ## Boundary Gate
 
-Check package versions before any edit. If all MSTest references are already 3.x
-and no v1/v2-to-v3 error is reported, state that migration is complete and make
-no changes. Do not consolidate working v3 packages into the metapackage. Run the
-existing tests only if verification was requested. This overrides all steps below.
+Check package versions before any edit. If all MSTest references are already 3.x,
+no v1/v2-to-v3 error is reported, and no `.testsettings` or `<LegacySettings>`
+remains, state that migration is complete and make no changes. A 3.x package
+version alone does not end the migration -- leftover v1/v2-era settings files or
+breaking-change errors are still in scope. Do not consolidate working v3 packages
+into the metapackage. Run the existing tests only if verification was requested.
+This overrides all steps below.
 
 ## Inputs
 

plugins/dotnet-test-migration/skills/migrate-mstest-v3-to-v4/SKILL.md

@@ -1,19 +1,20 @@
 ---
 name: migrate-mstest-v3-to-v4
 description: >
-  Fix build errors and breaking changes after upgrading MSTest from v3 to v4,
-  or plan a complete MSTest v3-to-v4 migration. Use when user says "upgrade to
+  Fix build errors and breaking changes after upgrading MSTest v3 to v4, or
+  plan a complete v3-to-v4 migration. Use when user says "upgrade to
   MSTest v4", "MSTest 4 migration", "MSTest v4 breaking changes", "tests don't
-  compile after upgrading MSTest", or has errors CS0507, CS0103, CS1061, CS1615 after updating MSTest packages from 3.x to 4.x.
-  USE FOR: Execute to ExecuteAsync, CallerInfo constructor on TestMethodAttribute,
+  compile after upgrading MSTest 3.x to 4.x", or hits CS0507, CS0103, CS1061, CS1615 after updating MSTest packages to 4.x.
+  USE FOR: Execute to ExecuteAsync, CallerInfo ctor on TestMethodAttribute,
   sealed custom attributes, ClassCleanupBehavior removal, TestContext.Properties
   Contains to ContainsKey, Assert.ThrowsException to ThrowsExactly,
-  Assert.IsInstanceOfType out parameter removal, ExpectedExceptionAttribute
+  Assert.IsInstanceOfType out param removal, ExpectedExceptionAttribute
   removal, TestTimeout enum removal, [TestMethod("name")] to DisplayName syntax,
   TreatDiscoveryWarningsAsErrors, TestContext.TestName in ClassInitialize,
   MSTest.Sdk MTP changes, dropped TFMs (net6.0/net7.0 to net8.0+).
-  DO NOT USE FOR: migrating from MSTest v1/v2 to v3 (use migrate-mstest-v1v2-to-v3
-  first), migrating between test frameworks, or general .NET upgrades.
+  DO NOT USE FOR: MSTest v1/v2 to v3, or errors left from a 2.x-to-3.x upgrade
+  (use migrate-mstest-v1v2-to-v3 first); test framework conversions; general
+  .NET upgrades.
 license: MIT
 ---